One of the fundamental data types in the Windows Runtime is the Guid. In most languages, it is represented as a binary-formatted data type like System.Guid or winrt::guid. But JavaScript doesn’t have a corresponding data type. So how are Windows Runtime Guids represented in JavaScript?
As strings.
But strings in a special format.
If a Windows Runtime function accepts a Guid, the JavaScript projection accepts a string in one of the following formats:
| Format | Description |
|---|---|
aaaaaaaabbbbccccddeeffgghhiijjkk |
Raw hex |
aaaaaaaa-bbbb-cccc-ddee-ffgghhiijjkk |
Hex with dashes |
(aaaaaaaa-bbbb-cccc-ddee-ffgghhiijjkk) |
Hex with dashes enclosed in parentheses |
{aaaaaaaa-bbbb-cccc-ddee-ffgghhiijjkk} |
Hex with dashes enclosed in braces |
{ 0xaaaaaaaa, 0xbbbb, 0xcccc, |
C initializer |
Letters a through k represent any hexadecimal digit. All parsing is case-insensitive. (That includes the x in the 0x of the C initializer format.)
In all cases, leading and trailing whitespace are ignored. A whitespace character is one which is classified as whitespace in Unicode version 6.2, which was the latest version of Unicode at the time JavaScript support was implemented.
| Character | Code point |
|---|---|
| CHARACTER TABULATION | U+0009 |
| LINE FEED | U+000A |
| LINE TABULATION | U+000B |
| FORM FEED | U+000C |
| CARRIAGE RETURN | U+000D |
| SPACE | U+0020 |
| NEXT LINE | U+0085 |
| NO-BREAK SPACE | U+00A0 |
| OGHAM SPACE MARK | U+1680 |
| MONGOLIAN VOWEL SEPARATOR | U+180E |
| EN QUAD | U+2000 |
| EM QUAD | U+2001 |
| EN SPACE | U+2002 |
| EM SPACE | U+2003 |
| THREE-PER-EM SPACE | U+2004 |
| FOUR-PER-EM SPACE | U+2005 |
| IX-PER-EM SPACE | U+2006 |
| FIGURE SPACE | U+2007 |
| PUNCTUATION SPACE | U+2008 |
| THIN SPACE | U+2009 |
| HAIR SPACE | U+200A |
| LINE SEPARATOR | U+2028 |
| PARAGRAPH SEPARATOR | U+2029 |
| NARROW NO-BREAK SPACE | U+202F |
| MEDIUM MATHEMATICAL SPACE | U+205F |
| IDEOGRAPHIC SPACE | U+3000 |
The MONGOLIAN VOWEL SEPARATOR is the odd one out: It was originally classified as whitespace but lost that status in Unicode 6.3.
Whitespace is permitted in the C initializer format anywhere, not just after commas. Strange but true.
Going the other way is much simpler: If a Windows Runtime function returns a Guid, the JavaScript version returns lowercase hex with dashes (no braces or parentheses).
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